The present invention relates generally to fire extinguishment systems and methods, and more particularly to an improved linear fire extinguisher system.
Linear fire extinguishment systems have been described in the prior art as useful for fire suppression in substantially closed spaces, such as vehicle engine compartments, aircraft engine nacelles, closed fuel storage areas, and the like. The prior art systems may be exemplified by that taught by Stewart et al (U.S. Pat. No. 5,909,776), and the references cited therein, which disclose a linear type fire extinguisher system including a sealed flexible plastic tube pressurized with gaseous extinguishant. The tube is routed in serpentine fashion throughout the compartment zone(s) to be protected from fire. When a fire on or near the protected compartment impinges on and locally heats a portion of the tube, the plastic weakens and ruptures at the heated portion and discharges the contents of the tube through the rupture onto the fire. Extinguishant discharge directly on the fire at its point of origin in the protected compartment is intended so that the amount of extinguishant available for discharge is efficiently used and storage of a quantity of extinguishant sufficient to flood the entire volume of the protected compartment is not necessary. The linear fire extinguisher structure is therefore useful in space critical applications such as vehicle engine compartments and aircraft engine nacelles. Because the linear extinguisher tube structure may be routed throughout very cluttered and widely spaced protected zones, the linear extinguisher may function as a fire detection system, an extinguishant reservoir and a discharge network in a single operationally reliable and cost and weight efficient system.
Prior art linear extinguisher structures suffer certain operational limitations principally because the tubes lack structure that would rupture predictably in response to the application of heat from a fire. Unsuccessful extinguishant discharge often results under some fire scenarios because of erratic tube rupture by splitting or cracking and subsequent inadequate, erratic and unpredictable extinguishant flow from the tube. After tube rupture, the extinguishant discharges substantially completely over a brief period of time, so if a persistent ignition source remains, such as a hot surface and residual combustible fluid, the fire may re-ignite after initial extinguishment.
The invention solves or substantially reduces in critical importance problems in the prior art as just described by providing an improved linear fire extinguisher structure including a plastic tube for containing and discharging extinguishant upon rupture of the tube, the tube having a multiplicity of selectively weakened pre-scored orifice patterns in the tube wall, the scored patterns having sufficient depth into the wall thickness to ensure preferential rupture at a scored pattern on heating, but without causing undesirable and premature discharge at heating temperatures or extinguishant pressures below predetermined desired threshold values. The invention also includes a coaxial tube structure in which an inner tube containing extinguishant is disposed within a second outer tube also containing extinguishant in the space between the inner and outer tubes, and wherein at least one of the inner and outer tube include a multiplicity of selectively weakened pre-scored orifice patterns, the outer tube initially rupturing and discharging extinguishant upon heating to initially extinguish the fire, and if the fire is not extinguished (or re-ignites) after initial discharge by the outer tube, the inner tube provides back-up linear extinguisher capability for the protected compartment(s). After thermal-induced rupture of the outer tube, residual extinguishant between the tubes may provide coolant to the inner tube to prevent premature rupture thereof.
The invention finds utility within substantially any enclosure where a fire may originate, and is especially useful in providing fire extinguishment capability in machinery enclosure applications where space is limited, such as aircraft engine nacelles, aircraft auxiliary power units and ground support equipment, vehicle engine compartments, ship engine or other machinery compartments, stationary turbines and other stationary power equipment, power equipment trailers and industrial machinery applications where liquid-fueled, oiled or hydraulically controlled equipment is operated.
It is therefore a principal object of the invention to provide an improved linear fire extinguisher system.
It is another object of the invention to provide a linear fire extinguisher having structure that ruptures predictably along its length upon the application of heat.
It is yet another object of the invention to provide a compact, light weight and inexpensive fire extinguisher system.
It is yet another object of the invention to provide a linear fire extinguisher system that ruptures and discharges extinguishant efficiently and reliably.
It is a further object of the invention to provide a linear fire extinguisher system with second time extinguishment capability in case of fire re-ignition.
These and other objects of the invention will become apparent as a detailed description of representative embodiments proceeds.